1. Field of the Invention
The present invention relates to a process of producing a hot dipped wire which is suitably used as a lead of an electronic component and a conductor of an electronic wiring, and more particularly but not exclusively relates to a process of fabricating a hot dipped tinned wire and a hot dipped solder plated wire.
2. Prior Art
A typical attempt of the conventional processes of producing hot dipped wires is illustrated in FIG. 5, in which a base wire to be plated undergoes wire drawing to produce a predetermine diameter wire 1' to be plated usually in a water soluble lubricant or an oil lubricant, using a wire drawing machine (not shown) including shoulder rollers, pulleys, a capstan, etc, all of which have wire passage surfaces made of iron materials. The drawn wire 1' to be plated is wound over a spool 2'. In the next step, the wire 1' to be plated which is unwound from the spool 2' is pulled through a steam annealing furnace 3' for annealing, and is then cleaned during traveling through a cleaning bath 5' using water 4'. Subsequently, the wire 1' to be plated is dried by heating in the dryer 6 to remove moisture on it, is passed through an acid flux bath 11 for acid cleaning the surface thereof, and is finally directly introduced with the acid flux adhering to it into a hot dipping metal bath 8, where the wire 1' to be plated makes contact with the molten metal for plating as well as cleaning the surface thereof. Then, the wire 1' to be plated passes through a drawing die d to produce a hot dipped wire 1'a.
Heretofore, iron materials were commonly used in shoulder rollers, pulleys, the capstan, etc of the wire drawing machine which define the wire drawing passage. For this reason, in the wire drawing step a trace amount of iron powder adheres to the surface of the wire 1' to be plated, which is then wound around a spool 2' with the iron powder adhered thereto. Furthermore, an iron spool is used as the spool 2'. Thus, the wire 1' to be plated is placed into contact with iron materials of the spool for a long period during of storage as well as during the wire drawing step.
Particularly, during the storage with the iron spool, the wire 1' to be plated is in contact with the iron materials of the body and the flange of the spool, and hence it is inevitable that iron oxides, such as an iron rust, adhere to the surface of the wire 1' to be plated. Such iron oxides provide very adverse influences in quality on the plated wire during the following hot dipping step. More specifically, the iron oxides adhering to the surface of the wire 1' to be plated change to iron hydroxides during travel in the steam annealing furnace 3' of the plating pretreatment step. When the wire 1' to be plated is introduced into the hot dipping bath 8, the iron hydroxides are decomposed to produce water, which is vaporized at once and dissipated from the surface of the wire 1' to be plated. As a result, nonplated portions are produced at surface portions of the wire 1' where the iron hydroxides had been adhered, and exposed surface portions are thus produced in the hot dipped wire.
Moreover, since the acid flux bath 11 is used in the plating pretreatment step, the acid is likely to scatter, and the acid flux adhered to the wire 1' to be plated is vaporized in the hot dipping bath 8 which is kept at a high temperature. These phenomena are liable to deteriorate or damage the equipment, and to pollute the working environment. Furthermore, the acid flux produces a metallic salt by reacting with the molten metal of the hot dipping bath, resulting in degradation of the hot dipping bath. Thus, the plating may also be deteriorated in quality.